1. Field of the Invention
The invention relates to a debarking machine for the preliminary debarking of logs prior to a separately performed final debarking, and more specifically to a debarking machine that includes a conveyor to store and feed logs.
2. Description of the Related Art
Debarking machines are disclosed e.g. in U.S. Pat. Nos. 4,685,498 and 5,394,912. A problem with the type of prior art debarking machines described in these patents is how to control the time that the logs to be debarked dwell or reside in the debarking machine. Excessive dwell time results in wood loss and, on the other hand, insufficient dwell time leaves too much bark on the logs. Dwell time should be readily changeable, depending e.g. on the type of wood to be barked and whether the wood is frozen or unfrozen.
Another drawback in the prior known solutions is that, due to the debarking machine having a closed end, the logs must be supplied into the debarking machine from above, i.e. the logs must be first hoisted up and then lowered or dropped into the debarking machine.
To eliminate these drawbacks, there is provided a debarking machine with an admission end provided with an opening for feeding logs into the debarking machine in a direction which corresponds to the advancing direction of the logs within the debarking machine itself. For feeding the logs, the debarking machine has its admission end provided with a conveyor adapted to positively feed the logs through the opening onto a lower portion of the chute of the debarking machine. Logs fed into the debarking machine displace logs previously fed in. By virtue of this arrangement, the rate of admission of logs into the debarking machine, as well as dwell time for logs in the debarking machine, can be readily controlled.
A debarking machine in accordance with the present invention may also be described as a debarking station in the path of a wood flow. Wood support surfaces extend above the conveyor to form a chute for supporting logs piled on the conveyor. This pile of logs forms a reservoir of wood to be fed into the debarking station. The chute has a similar cross-sectional shape to a chute defined by support surfaces in the debarking station and is aligned with the debarking station such that wood on the conveyor moves straight into the debarking station. The invention transforms what was a batch debarking process in the prior art into a continuous process.
The advancement of logs through a debarking machine can be made totally dependent upon the positive feed of a conveyor functioning as a supply system for the debarking machine. Another way of designing a debarking machine is of course that the debarking machine itself provides either an encouraging or discouraging effect on the advancement of logs, e.g., by adjusting the inclination of the debarking machine as is known in the art.
The conveyor has a feed rate and, if necessary, also a feed force that can be regulated. At its simplest, the feed rate regulation may comprise a mere switch for switching the conveyor on or off. In one preferred embodiment of the invention, the conveyor is adapted to store logs to be fed into the debarking machine. Thus, logs can be supplied onto the conveyor at highly irregular intervals while maintaining a constant wood flow into the debarking machine itself. Another influencing factor in terms of the operation of a debarking machine is the thickness of a layer of logs supplied onto the conveyor.
The maximum distance of an active conveyor section from the admission end of a debarking machine is preferably less than the average length of logs to be barked in the debarking machine. Proper selection of this distance in accordance with the average length of a log ensures reliable feeding of logs by means of the conveyor. For the same reason, the conveyor has its feeding direction and profile arranged in view of allowing also a free movement upstream of a debarking machine.
A guide element is preferably provided between the conveyor and the debarking machine. The guide element comprising one or more guide surfaces for delivering logs into the debarking machine. To ensure proper guidance for the logs, the guide surface of the guide element is preferably designed to have a width transverse to the feed direction that is substantially equal to the cross-sectional width of the admission end opening at a position corresponding to the log entry point.
The opening provided in the admission end of the debarking machine is configured substantially equal to the size and shape of a chute formed by the support surfaces present in the debarking machine, upon which the logs to be processed travel through the debarking machine. The conveyor chute and debarker chute form a substantially continuous trough.